Portable digital telephones often operate by coding voice using a so called xe2x80x9ccodecxe2x80x9d device or voice coder (xe2x80x9cvocoderxe2x80x9d). The codec breaks down the voice into digital parameters that indicate the voice. In order to reduce the size of the data, the information is processed in a way that removes the portions of the sound that the user is least likely to hear. The coding is generally done on a statistical basis, as a function of frequency.
The inventor recognized, however, that the average device of this type is based on the characteristics of an average person. Different people hear differently. Hearing depends on age, race, sex and other information. It may also depend on the person""s occupation. For example, certain professions can cause more hearing loss than others.
The telephones use a codec to code and decode sound. However, the coding scheme in the codecs is set for an average person.
The present system describes changing characteristics of the coding carried out by a codec to compensate for a person""s individual hearing capabilities. According to the present system, an indication of a person""s hearing capabilities are obtained. This indication can include one of a number of presets, or can be a custom determination of a person""s actual hearing. The system determines how to adjust the output sound so that the user will be better able to hear it.
A message is sent from the decoding phone to the coding phone telling the far-end codec to alter certain frequencies to put more information in those frequencies. Then, on decompression, the user obtains pre-emphasized signals.